Gravitational dynamics of large stellar systems

McMillan, Stephen L. W.

doi:10.1088/0264-9381/25/11/114007

Cited by 5 publications

(7 citation statements)

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“…12). S 1 and S 2 also register an initial core collapse connected with mass segregation (rapid decrease for 3%, 5%, and 10% Lagrangian radii) in agreement with previous numerical work ( Portegies Zwart & McMillan 2002;Portegies Zwart et al 2004;Gürkan et al 2004;McMillan 2008). On the other hand, S 3 does not show any indication of core collapse.…”

Section: Cluster Evolutionsupporting

confidence: 90%

Intermediate Mass Black Hole Formation in compact Young Massive Star Clusters

Rizzuto,

Naab,

Spurzem

et al. 2020

Preprint

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Young dense massive star clusters are a promising environment for the formation of intermediate mass black holes (IMBHs) through collisions. We present a set of 80 simulations carried out with Nbody6++GPU of 10 initial conditions for compact ∼ 7 × 10 4 M star clusters with half-mass radii R h 1pc, central densities ρ core 10 5 M pc −3 , and resolved stellar populations with 10% primordial binaries. Very massive stars (VMSs) with masses up to ∼ 400M grow rapidly by binary exchange and three-body scattering events with main sequences stars in hard binaries. Assuming that in VMS -stellar BH collisions all stellar material is accreted onto the BH, IMBHs with masses up to M BH ∼ 350M can form on timescales of 15 Myr. This process was qualitatively predicted from Monte Carlo MOCCA simulations. Despite the stochastic nature of the process -typically not more than 3/8 cluster realisations show IMBH formation -we find indications for higher formation efficiencies in more compact clusters. Assuming a lower accretion fraction of 0.5 for VMS -BH collisions, IMBHs can also form. The process might not work for accretion fractions as low as 0.1. After formation, the IMBHs can experience occasional mergers with stellar mass BHs in intermediate mass-ratio inspiral events (IMRIs) on a 100 Myr timescale. Realised with more than 10 5 stars, 10 % binaries, the assumed stellar evolution model with all relevant evolution processes included and 300 Myr simulation time, our large suite of simulations indicates that IMBHs of several hundred solar masses might form rapidly in massive star clusters right after their birth while they are still compact.

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Section: Cluster Evolutionsupporting

confidence: 90%

Intermediate Mass Black Hole Formation in compact Young Massive Star Clusters

Rizzuto,

Naab,

Spurzem

et al. 2020

Preprint

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“…One could also argue that the precursors of the old (globular) clusters might have been very different from the young clusters today. High densities might even be essential to enable runaway mergers as a pathway to produce intermediate black holes (IMBHs) in globular clusters (McMillan 2008). McMillan (2008) gives the example that a mean density of ∼ 5 · 10 7 M pc −3 would be required for a cluster with a half-mass radius of 0.2 pc.…”

Section: Independent Emacss-mcmc Runsmentioning

confidence: 99%

“…High densities might even be essential to enable runaway mergers as a pathway to produce intermediate black holes (IMBHs) in globular clusters (McMillan 2008). McMillan (2008) gives the example that a mean density of ∼ 5 · 10 7 M pc −3 would be required for a cluster with a half-mass radius of 0.2 pc. Moreover, Pfalzner et al (2014) ran semi-analytical models for the formation of star clusters and show that the central cluster area can have stellar densities of ∼ 4 · 10 5 M pc −3 at the moment of gas expulsion; see Figure 2 of Pfalzner et al (2014).…”

Section: Independent Emacss-mcmc Runsmentioning

confidence: 99%

“…As a comparison we also plot the minimum densities a cluster needs to have in order to be stable against the tidal disruption of a galaxy (ρ hm ∼ 0.1 M pc −3 (Bok 1934), green triangle line) and against passing giant molecular clouds (ρ hm ∼ 10 M pc −3(Spitzer 1958), cyan star line). The turquoise hexagon line shows a mean density of ∼ 5 · 10 7 M pc −3 that might be required for a cluster with a half-mass radius of 0.2 pc to form an IMBH via a runaway merger(McMillan 2008). We furthermore show the range of observed half-mass densities for globular clusters, ρ hm ∼ 10 −2−3.7 M pc −3 , (red shaded region) and the range of present-day observed half-mass densities for clusters younger than 10 Myr (ρ hm ∼ 10 2−4 M pc −3 (Portegies Zwart et al 2010) (blue shaded region); the purple shaded region is the overlap of these blue and red regions.…”

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confidence: 99%

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The initial conditions of observed star clusters – I. Method description and validation

Pijloo¹,

Zwart²,

Alexander³

et al. 2015

Mon. Not. R. Astron. Soc.

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We have coupled a fast, parametrized star cluster evolution code to a Markov Chain Monte Carlo code to determine the distribution of probable initial conditions of observed star clusters, which may serve as a starting point for future N -body calculations. In this paper we validate our method by applying it to a set of star clusters which have been studied in detail numerically with N -body simulations and Monte Carlo methods: the Galactic globular clusters M4, 47 Tucanae, NGC 6397, M22, ω Centauri, Palomar 14 and Palomar 4, the Galactic open cluster M67, and the M31 globular cluster G1. For each cluster we derive a distribution of initial conditions that, after evolution up to the cluster's current age, evolves to the currently observed conditions. We find that there is a connection between the morphology of the distribution of initial conditions and the dynamical age of a cluster and that a degeneracy in the initial half-mass radius towards small radii is present for clusters which have undergone a core collapse during their evolution. We find that the results of our method are in agreement with N -body and Monte Carlo studies for the majority of clusters. We conclude that our method is able to find reliable posteriors for the determined initial mass and half-mass radius for observed star clusters, and thus forms an suitable starting point for modeling an observed cluster's evolution.

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“…The presence of an IMBH in a globular cluster has important consequences for the cluster's structure, kinematics, internal energetics and long-term dynamical evolution (see e.g. Baumgardt et al 2004, Heggie et al 2007, Trenti et al 2007, Miocchi 2007; see also McMillan 2008 for a review). In addition, Eddington accretion onto IMBHs has been proposed as the mechanism powering some ultraluminous X-ray sources (e.g.…”

Section: Introductionmentioning

confidence: 99%

Intermediate-Mass Black Holes in Early Globular Clusters

Vesperini

McMillan

D’Ercole

et al. 2010

ApJ

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Spectroscopic and photometric observations show that many globular clusters host multiple stellar populations, challenging the common paradigm that globular clusters are "simple stellar populations" composed of stars of uniform age and chemical composition. The chemical abundances of secondgeneration (SG) stars constrain the sources of gas out of which these stars must have formed, indicating that the gas must contain matter processed through the high-temperature CNO cycle. First-generation massive Asymptotic Giant Branch (AGB) stars have been proposed as the source of this gas. In a previous study, by means of hydrodynamical and N-body simulations, we have shown that the AGB ejecta collect in a cooling flow in the cluster core, where the gas reaches high densities, ultimately forming a centrally concentrated subsystem of SG stars. In this Letter we show that the high gas density can also lead to significant accretion onto a pre-existing seed black hole. We show that gas accretion can increase the black hole mass by up to a factor of 100. The details of the gas dynamics are important in determining the actual black hole growth. Assuming a near-universal seed black hole mass and small cluster-to-cluster variations in the duration of the SG formation phase, the outcome of our scenario is one in which the present intermediate-mass black hole (IMBH) mass may have only a weak dependence on the current cluster properties. The scenario presented provides a natural mechanism for the formation of an IMBH at the cluster center during the SG star-formation phase.

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Gravitational dynamics of large stellar systems

Cited by 5 publications

References 87 publications

Intermediate Mass Black Hole Formation in compact Young Massive Star Clusters

Intermediate Mass Black Hole Formation in compact Young Massive Star Clusters

The initial conditions of observed star clusters – I. Method description and validation

Intermediate-Mass Black Holes in Early Globular Clusters

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